The invention disclosed and claimed herein generally pertains to automatic tool changing apparatus of the type which is used to change all of the tools in a multiple-spindle machining center simultaneously. More particularly, the invention pertains to apparatus of the above type wherein the axes of all the tools dedicated for use by a particular spindle of the machining center are maintained in a common plane as such tools are respectively stored in a magazine, moved between the magazine and the particular spindle, or inserted into the particular spindle for use in a machining operation. Even more particularly, the invention pertains to apparatus of the above type wherein a number of tool carrying devices, one dedicated to each spindle, are constrained to rotate around a common axis during a tool change operation, the spindles and magazines remaining immobile during such operation.
Devices for automatically and simultaneously changing all of the tools in a multiple-spindle machining center are by now well known in the art. One of the first of such devices is shown in U.S. Pat. No. 3,571,912, which was issued Mar. 23, 1971 to Mr. Ervin J. Kielma, inventor of the present invention. Another of such prior art devices is disclosed in U.S. Pat. No. 4,227,296, issued Oct. 14, 1980 to Eduard Wittenbreder.
In a standard arrangement for such tool changing devices, as taught by the above art, a tool storage unit is positioned adjacent to a machining center or machine tool which has two or more spindles. The tool storage unit is provided with a number of magazines which are generally in spaced-apart parallel relationship with one another, the spindles of the machining center also being in parallel relationship with one another. A number of tool carrying members are mounted along a row, each member corresponding to one of the magazines and also to one of the spindles. Each member is provided with two opposingly directed arms, a tool grip element being attached to the end of each arm of each member.
In some prior art devices of the above type, it is necessary to move or manuever the magazines or spindles, relative to one another, in order for a tool change operation to take place. In other of such prior art devices, the tool carrying members, aligned in a row as aforesaid, must be rotated through one or more 180.degree. arcs around separate axes, as each tool change operation is performed. In order to prevent interferences between adjacent members and tools carried thereby during rotations, a minimum spacing must be maintained between adjacent members. Such condition may, in turn, impose a minimum spacing limitation upon the spindles of the machining center. In order to achieve compatability between the machining center and the tool change device, it could be necessary to locate the spindles of the center so far apart from one another that certain machining operations could not be performed by the center. Also, the minimum spacing or separation of the spindles could thereby be made significantly greater than the spacing which would be required only by the dimensions of the spindles and spindleheads of the center.
The present invention provides apparatus for changing tools in a multiple-spindle machining center wherein a number of tool change carriers are constrained to rotate about a common axis during a tool change operation. The carriers are further constrained to linearly translate along first and second axes, which are orthogonal to one another and to the common axis. By employing such apparatus, tools may be exchanged between the spindles of the center and magazines of an adjacent tool storage unit without moving either the spindles of the unit. In addition, the spacing which must be maintained between tool carriers of such apparatus, to prevent interference between the carriers during rotations, is substantially diminished in comparison with the spacing between carriers which are required in prior art devices. It is anticipated that an embodiment of the present invention may be employed to automatically and simultaneously change tools in a multiple-spindle machining center wherein the minimum spacing between spindles is determined only by the geometry and dimensions of the spindles and spindleheads. However, it is by no means intended to limit the invention to such embodiment.